1. Field of the Invention
The present invention relates to centrifuges and more particularly, to an improved hard surfaced centrifuge screw conveyor.
2. Description of Related Art
One significant problem with separating centrifuges is the wear of the helical conveyor blades by abrasive solids. Although the conveyor blades are typically fabricated from hard-wear steel alloys, abrasive solids can cause such wear in the critical solids contacting area so as to alter blade surface characteristics and clearance from the surrounding wall of the centrifuge bowl.
Wear-resistant members which are attached to the conveyor blades are utilized to prevent wear of the helical conveyor blades. However, it has been found that conventional wear-resistant members are difficult to install and remove. One attempt at solving the aforementioned problem of screw conveyor blade wear is disclosed is U.S. Pat. No. 4,328,925 entitled "Hard Surfacing for a Centrifuge Conveyor" issued May 11, 1982 to Shapiro ("'925 patent"). The '925 patent discloses one embodiment which utilizes a dovetail groove formed in a backing tile, which is fixed to the conveyor distal surface, and a complimentarily configured dovetail portion of an abrasion-resistant member slidably engaged therein. The axes of the dovetail groove and complimentary dovetail portion are parallel to the helical blade and therefore, follows the helix of the conveyor. It has been found that such a configuration presents great difficulty in removing and installing the abrasion-resistant members due to the difficulty for technicians to correctly position their tools when attempting to replace the abrasion resistant members. Furthermore, the aforementioned dovetail grooves disclosed in the '925 patent cannot be formed in short conveyor flights such as in decanter-type centrifuges. Additionally, it has been found that since the grooves follow the helix and thus, generally follow the direction of rotation of the conveyor, the tiles mounted to the conveyor are prone to moving in a direction parallel to the conveyor blade during rotation of the conveyor. Such tiles have also become unattached from the blade during rotation of the conveyor. In another embodiment, the '925 patent discloses an abrasion-resistant surface assembly comprising a backing tile, which is welded to the flight of the screw conveyor, and an abrasion-resistant member which is secured to the backing tile via a wedge plate acting in conjunction with a screw. However, such a configuration cannot be utilized with conveyor flights of minimum height.
Another attempt to solve the aforementioned problems is to braze tungsten carbide tiles to the conveyor blade or flight. However, it has been found that such a configuration results in cracked and damaged tungsten tiles that could disintegrate during operation of the centrifuge. A further attempt to solve the aforementioned problems is to epoxy wear-resistant or abrasion resistant tiles to the conveyor flights. However, it has been found that the epoxy bond cannot withstand the centrifugal force produced by the rotating conveyor.
It has also been found that conventional hard or wear-resistant surfacing cannot withstand high magnitude centrifugal forces produced by conveyors that operate at high r.p.m. (revolutions per minute), i.e., 6,000 r.p.m.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a new and improved hard surfacing for a centrifuge screw conveyor that can be utilized in conjunction with conveyor flights of minimum height.
It is another object of the present invention to provide a new and improved hard surfaced centrifuge screw conveyor having wear-resistant members mounted on the conveyor and which can be easily removed and installed without incurring unnecessary expense and centrifuge down time.
It is a further object of the present invention to provide a new and improved hard surfacing for a centrifuge screw conveyor that can be manufactured at a reasonable cost.
It is another object of the present invention to provide a new and improved hard surfacing that can be applied to existing centrifuge screw conveyors.
It is a further object of the present invention to provide a new and improved hard surfaced centrifuge screw conveyor having wear-resistant members mounted on the conveyor which remain secure during operation of the centrifuge and can withstand extreme magnitudes of centrifugal force.
It is yet another object of the present invention to provide a new and improved method for applying hard surfacing to existing centrifuge screw conveyors at a reasonable cost.